The atmospheric methane (CH
4
) burden is rising sharply, but the causes are still not well understood. One factor of uncertainty is the importance of tropical CH
4
emissions into the global mix. Isotopic signatures of major sources remain poorly constrained, despite their usefulness in constraining the global methane budget. Here, a collection of new
δ
13
C
CH
4
signatures is presented for a range of tropical wetlands and rice fields determined from air samples collected during campaigns from 2016 to 2020. Long-term monitoring of
δ
13
C
CH
4
in ambient air has been conducted at the Chacaltaya observatory, Bolivia and Southern Botswana. Both long-term records are dominated by biogenic CH
4
sources, with isotopic signatures expected from wetland sources. From the longer-term Bolivian record, a seasonal isotopic shift is observed corresponding to wetland extent suggesting that there is input of relatively isotopically light CH
4
to the atmosphere during periods of reduced wetland extent. This new data expands the geographical extent and range of measurements of tropical wetland and rice
δ
13
C
CH
4
sources and hints at significant seasonal variation in tropical wetland
δ
13
C
CH
4
signatures which may be important to capture in future global and regional models.
This article is part of a discussion meeting issue ‘Rising methane: is warming feeding warming? (part 2)’.